1. Field of the Invention
This invention relates generally to a system and method for processing the electric signals from a plurality of fuel cells utilizing one circuit board and, more particularly, to a system and method for processing the electric signals from a plurality of fuel cells utilizing one circuit board connected to a conductive compressible connector or connected directly to bipolar plates by plate contactors.
2. Discussion of the Related Art
Hydrogen is a very attractive fuel because it is clean and can be used to efficiently produce electricity in a fuel cell. A hydrogen fuel cell is an electro-chemical device that includes an anode and a cathode with an electrolyte therebetween. The anode receives hydrogen gas and the cathode receives oxygen or air. The hydrogen gas is dissociated in the anode side catalyst to generate free protons and electrons. The protons pass through the electrolyte to the cathode. The protons react with the oxygen and the electrons in the cathode side catalyst to generate water. The electrons from the anode cannot pass through the electrolyte, and thus are directed through a load to perform work before being sent to the cathode.
Proton exchange membrane fuel cells (PEMFC) are a popular fuel cell for vehicles. The PEMFC generally includes a solid polymer electrolyte proton conducting membrane, such as a perfluorosulfonic acid membrane. The anode and cathode electrodes (catalyst layers) typically include finely divided catalytic particles, usually platinum (Pt), supported on carbon particles and mixed with an ionomer. The catalytic mixture is deposited on opposing sides of the membrane. The combination of the anode catalytic mixture, the cathode catalytic mixture and the membrane define a membrane electrode assembly (MEA). Each MEA is usually sandwiched between two sheets of porous material, a gas diffusion layer (GDL), that protects the mechanical integrity of the membrane and helps in uniform reactant and humidity distribution. The part of the MEA that separates the anode and cathode flows is called the active area, and only in this area the water vapors can be freely exchanged between the anode and cathode. MEAs are relatively expensive to manufacture and require certain humidification conditions for effective operation.
Fuel cells are typically comprised of a plurality of electrically conductive unipolar and bipolar plates alternatively assembled (stacked) with a plurality of MEAs, electrodes, gaskets, seals and gas diffusion media (also known as “softgoods”). Several fuel cells are typically combined in a fuel cell stack to generate the desired power. For example, a typical fuel cell stack for a vehicle may have two hundred or more stacked fuel cells. The fuel cell stack receives a cathode input reactant gas, typically a flow of air forced through the stack by a compressor. Not all of the oxygen is consumed by the stack and some of the air is output as a cathode exhaust gas that may include water as a reaction by-product. The fuel cell stack also receives an anode hydrogen reactant gas that flows into the anode side of the stack. The stack also includes flow channels through which a cooling fluid flows.
A fuel cell stack includes a series of bipolar plates (separators) positioned between the several MEAs in the stack, where the bipolar plates and the MEAs are positioned between the two end plates. The bipolar plates include anode side and cathode side flow distributors (flow fields) for adjacent fuel cells in the stack. Anode gas flow channels are provided on the anode side of the bipolar plates that allow the anode reactant gas to flow to the respective MEA. Cathode gas flow channels are provided on the cathode side of the bipolar plates that allow the cathode reactant gas to flow to the respective MEA. One end plate includes anode gas flow channels, and the other end plate includes cathode gas flow channels. The bipolar plates and end plates are made of a conductive material, such as stainless steel or a conductive composite. After stacking, these components are typically placed under compression to minimize electrical contact resistances and to close the seals. The end plates conduct the electricity generated by the fuel cells out of the stack. The bipolar plates also include flow channels through which a cooling fluid flows.
It is known in the art to process the electric signals from certain plates in a fuel cell system to determine whether the fuel cell stack is functioning properly and to perform cell-to-cell short-circuiting, as is known to those having skill in the art. Typically, electric signal processing is done every other cell because of the costs associated with monitoring every cell. Furthermore, it can be difficult to provide the necessary components in the space available to process the electric signal from every cell. There is a need in the art for processing the electric signal from every cell while minimizing the cost and space requirements associated therewith.